/*
 * ProGuard -- shrinking, optimization, obfuscation, and preverification of Java bytecode.
 *
 * Copyright (c) 2002-2018 GuardSquare NV
 *
 * This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public
 * License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later
 * version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied
 * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along with this program; if not, write to the Free
 * Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */
package proguard.optimize;

import proguard.classfile.*;
import proguard.classfile.attribute.*;
import proguard.classfile.attribute.visitor.AttributeVisitor;
import proguard.classfile.constant.*;
import proguard.classfile.constant.visitor.ConstantVisitor;
import proguard.classfile.editor.CodeAttributeEditor;
import proguard.classfile.instruction.*;
import proguard.classfile.instruction.visitor.InstructionVisitor;
import proguard.classfile.util.*;
import proguard.classfile.visitor.MemberVisitor;

/**
 * This AttributeVisitor adds an additional integer parameter to the tweaked initialization method invocations that it
 * visits.
 */
public class DuplicateInitializerInvocationFixer extends SimplifiedVisitor
    implements AttributeVisitor, InstructionVisitor, ConstantVisitor, MemberVisitor {
    private static final boolean DEBUG = false;

    private final InstructionVisitor extraAddedInstructionVisitor;

    private final CodeAttributeEditor codeAttributeEditor = new CodeAttributeEditor();

    private String descriptor;
    private int descriptorLengthDelta;

    /**
     * Creates a new DuplicateInitializerInvocationFixer.
     */
    public DuplicateInitializerInvocationFixer() {
        this(null);
    }

    /**
     * Creates a new DuplicateInitializerInvocationFixer.
     * 
     * @param extraAddedInstructionVisitor an optional extra visitor for all added instructions.
     */
    public DuplicateInitializerInvocationFixer(InstructionVisitor extraAddedInstructionVisitor) {
        this.extraAddedInstructionVisitor = extraAddedInstructionVisitor;
    }

    // Implementations for AttributeVisitor.

    public void visitAnyAttribute(Clazz clazz, Attribute attribute) {}

    public void visitCodeAttribute(Clazz clazz, Method method, CodeAttribute codeAttribute) {

        // Reset the code changes.
        codeAttributeEditor.reset(codeAttribute.u4codeLength);

        // Fix any duplicate constructor invocations.
        codeAttribute.instructionsAccept(clazz, method, this);

        // Apply all accumulated changes to the code.
        codeAttributeEditor.visitCodeAttribute(clazz, method, codeAttribute);
    }

    // Implementations for InstructionVisitor.

    public void visitAnyInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset,
        Instruction instruction) {}

    public void visitConstantInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset,
        ConstantInstruction constantInstruction) {
        if (constantInstruction.opcode == InstructionConstants.OP_INVOKESPECIAL) {
            descriptorLengthDelta = 0;
            clazz.constantPoolEntryAccept(constantInstruction.constantIndex, this);

            if (descriptorLengthDelta > 0) {
                Instruction extraInstruction = new SimpleInstruction(descriptorLengthDelta == 1
                    ? InstructionConstants.OP_ICONST_0 : InstructionConstants.OP_ACONST_NULL);

                codeAttributeEditor.insertBeforeInstruction(offset, extraInstruction);

                if (DEBUG) {
                    System.out.println("  [" + clazz.getName() + "." + method.getName(clazz)
                        + method.getDescriptor(clazz) + "] Inserting " + extraInstruction.toString() + " before "
                        + constantInstruction.toString(offset));
                }

                if (extraAddedInstructionVisitor != null) {
                    extraInstruction.accept(null, null, null, offset, extraAddedInstructionVisitor);
                }
            }
        }
    }

    // Implementations for ConstantVisitor.

    public void visitAnyMethodrefConstant(Clazz clazz, RefConstant refConstant) {
        // Check the referenced constructor descriptor.
        if (refConstant.getName(clazz).equals(ClassConstants.METHOD_NAME_INIT)) {
            descriptor = refConstant.getType(clazz);

            refConstant.referencedMemberAccept(this);
        }
    }

    // Implementations for MemberVisitor.

    public void visitLibraryMethod(LibraryClass libraryClass, LibraryMethod libraryMethod) {}

    public void visitProgramMethod(ProgramClass programClass, ProgramMethod programMethod) {
        descriptorLengthDelta = programMethod.getDescriptor(programClass).length() - descriptor.length();

        if (DEBUG) {
            if (descriptorLengthDelta > 0) {
                System.out.println("DuplicateInitializerInvocationFixer:");
                System.out.println("  [" + programClass.getName() + "." + programMethod.getName(programClass)
                    + programMethod.getDescriptor(programClass) + "] ("
                    + ClassUtil.externalClassAccessFlags(programMethod.getAccessFlags()) + ") referenced by:");
            }
        }
    }
}
